Low voltage light drivers and ballasts do not have identical relationships between an applied dimming signal and the power drawn by the combination of the driver/ballast and the connected lights. Consequently, replacing a driver/ballast with a comparable part will result in different dimming performance making it time consuming to replace a driver/ballast and reconfigure the system to obtain optimal dimmer performance.
This situation is complicated by the fact that low voltage light drivers and ballasts have different non-linear relationships between the applied dimming signal and the power drawn by the combination of the driver/ballast and the connected lights. In some cases the low end of the driver's dimming range may be at about 1 VDC output of the 0-10V output range from a dimmer controller. Similarly, the high end of the driver's dimming range may be at about 8.6 VDC of the 0-10V output range of the dimmer controller. In this example, the dimming range between 0 and 1 VDC and from 8.6 VDC and 10 VDC is known as dead travel.
Determination of ballast or driver performance to guarantee the 1-100% dimmer position values match with the maximum and minimum power output of a particular driver/ballast are typically accomplished by eye or via a light meter. The operation is inaccurate and must be performed manually. This is time consuming for an installer. This performance matching is also limited to the ballast/driver and the lights it is combined with. All ballasts and drivers are not identical and after installation, replacement of a light will destroy any correspondence between the light performance and the dimmer control setting.